Treatment of Subterranean Formations

ABSTRACT

A method of preparing and using a subterranean formation stabilization agent. The stabilization agent includes a guanidyl copolymer and may be admixed with a fracturing fluid and optionally brine. The stabilization agent is effective in preventing and/or reducing, for example, clay swelling and fines migration from a subterranean formation contacted with the stabilization agent.

CROSS-REFERENCE

A benefit of priority is claimed to U.S. Provisional Patent ApplicationNo. 61/384,974 filed 21 Sep., 2010, the disclosure of which isincorporated herein in its entirety.

FIELD OF DISCLOSURE

The present disclosure relates, generally, to the stabilization ofsubterranean formations by the addition of a guanidyl copolymer to thesubterranean formation. The disclosure further relates to materials andmethods for stabilizing subterranean formations, for example, byreducing clay swelling and/or fines migration.

BRIEF DESCRIPTION OF RELATED TECHNOLOGY

The production of hydrocarbons from subterranean formations is ofteneffected by the presence of clays and other fines, which can migrate andplug off or restrict the flow of the hydrocarbon product. The migrationof fines in a subterranean formation is often the result of clayswelling, salt dissolution, and/or the disturbance of fines by theintroduction of fluids that are foreign to the formation. Typically, aforeign fluid (e.g., fracturing fluid or stabilizing fluid) isintroduced into the formation for the purpose of completing and/ortreating the formation to stimulate production of hydrocarbons by, forexample, fracturing, acidizing, or stabilizing the well.

The fracturing fluids used throughout the oil and gas industry are basedon a low-cost anionic friction reducer in combination with a claystabilizer (e.g., choline chloride and/or trimethylamine). Thesefracturing fluids work adequately in formations where there is arelative high level of permeability, expressed in millidarcy.

The anionic friction reducer facilitates the fracturing of thesubterranean formation by allowing the system to achieve a desiredpressure in the fracturing zone and the choline chloride and/ortrimethylamine help prevent the components of the formation (e.g., thesand and/or clay) from swelling and/or migrating while they are incontact with the fracturing fluids. Once the addition of fracturingfluid and thereby the choline chloride and/or trimethylamine is halted,they dilute out, and the components of the formation begin to swelland/or migrate in the reservoir water thereby reducing the permeabilityof the formation and the rate of hydrocarbon production. Due to thistime limited effect, choline chloride and trimethylamine are oftenreferred to as temporary clay stabilizers.

The composition and behavior of shale formations are notably differentthan those made of sand and/or clay. Shale consists of extremely fine(micron to submicron sized) particulates that are held together withwater soluble salts (e.g., calcium chloride and/or barium chloride).Typically, shale formations have very low levels of permeability (oftenexpressed in terms of microdarcy or nanodarcy (i.e., factors of 1000lower than clay or sand formations) due to the extremely tight packingof its component minerals.

In shale formations, fracturing water or reservoir water dissolves watersoluble minerals causing the formation to lose its structural integrityand plug the fractured zone with fines. Correspondingly, temporary claystabilizers (e.g., choline chloride and/or trimethylamine) havedisplayed little effect on shale stability and cores start to plugshortly after the injection of water solutions containing low and evenhigh concentrations (or percentages) of temporary clay stabilizers.

Notably, plugging of the core mirrors events happening during and afterthe fracturing of the shale formation. Fracturing the shale formationincludes forcing millions of gallons of water into the shale (whichdissolves the water-soluble salts and the shale begins to collapse),then removing the water of which less than 10% to 15% is typicallyrecovered. This recovered water contains high levels of fine, suspendedmaterial, indicative of the collapse of the shale structure and theproduction of huge amounts of fines. Hydrocarbon production (e.g.,natural gas and/or oil) from these systems might be steady for a shortperiod but then rapidly declines, indicative of the disintegration ofthe formation and blockage of the fractured area.

A fracturing fluid that includes a permanent clay stabilizer, thatadditionally stabilizes shale formations, could increase hydrocarbonproduction, increase the amount of recovered water, and reduce the finescontent of this water.

SUMMARY

In one embodiment, a subterranean formation can be stabilized bycontacting the formation with a stabilization agent that includes aguanidyl copolymer. In one instance, the stabilization agent includes awater-soluble salt, for example, in a weight ratio of about 10:1 toabout 1:10, grams guanidyl copolymer to grams water-soluble salt. Inanother instance, the stabilization agent includes a water-solublefriction reducer, for example, in a ratio of about 10:1 to about 1:10,grams guanidyl copolymer to grams water-soluble friction reducer. In yetanother instance, the stabilization agent includes a friction reducer, awater-soluble salt and the guanidyl copolymer.

In another embodiment, the formation can be stabilized by mixing thestabilizing agent with a fracturing fluid, and contacting the formationwith the fracturing fluid/stabilizing agent combination. The flow ofhydrocarbon product from the subterranean formation contacted with themixture of a guanidyl copolymer stabilizing agent and a fracturing fluidcan be higher than the flow from the subterranean formation contactedwith a fracturing fluid free of the stabilization agent. Furthermore,the hydrocarbon product can be free of, or include fewer particles fromthe subterranean formation (e.g., fines) than the hydrocarbon productfrom the subterranean formation contacted with the fracturing fluid freeof the stabilization agent.

In another embodiment, hydrocarbon production can be increased bycontacting the subterranean formation with a stabilization agent. In oneinstance, clay swelling and/or fines migration can be reduced bycontacting the subterranean formation with a stabilization agent thatcomprises a guanidyl copolymer. In another instance, the stabilizationagent also includes a cationic friction reducer. In still anotherinstance, a well from which hydrocarbons have been extracted can berestabilized by contacting the hydraulically fractured subterraneanformation with the stabilization agent. In yet another instance,hydrocarbons can be extracted from an oil containing subterraneanformation comprising by providing, through a first borehole, apressurized floodwater that comprises about 50 ppm to about 5,000 ppm,about 100 ppm to about 1,000 ppm, or about 200 ppm to about 600 ppm of aguanidyl copolymer; and recovering oil from the subterranean formationthrough a second borehole.

In still another embodiment, a bore hole can be flushed with a drillingfluid that comprises a guanidyl copolymer.

DETAILED DESCRIPTION

Disclosed herein is a permanent subterranean stabilization agent thatincludes a cationic polymer that is effective in low concentrations, anda method of using this stabilization agent for the production ofhydrocarbons from subterranean formations. Herein, “permanent” meansthat the stabilization of the subterranean formation (as a function oftime) is not dependent on the continued addition of the stabilizationagent, preferably the subterranean formation remains stable forhydrocarbon production for at least one month after removal of thefracturing fluids that typically contain the stabilization agent. Thesubterranean formation can include clay, shale, sand, rock, solids addedto the formation, and any other material encountered when drilling ahydrocarbon well.

The compounds, compositions and methods described herein may beunderstood more readily by reference to the following detaileddescription and the examples provided. It is to be understood that thisinvention is not limited to the specific components, articles, processesand/or conditions described, as these may, of course, vary. It is alsoto be understood that the terminology used herein is for the purpose ofdescribing particular embodiments only and is not intended to belimiting.

Ranges may be expressed herein as from “about” or “approximately” oneparticular value or to “about” or “approximately” another particularvalue. When such a range is expressed, another embodiment includes fromthe one particular value or to the other particular value. Similarly,when values are expressed as approximations, by use of the antecedent“about,” it will be understood that the particular value forms anotherembodiment.

In one embodiment, a stabilization agent includes a guanidyl copolymerthat can be prepared, for example, from the condensation polymerizationof a guanidyl reactant and a carbonyl reactant, see for example, U.S.Pat. No. 5,659,011 incorporated herein by reference in its entirety. Inanother embodiment, the guanidyl copolymer can be prepared from thecondensation polymerization of a guanidyl reactant and an iminereactant. Typically, a condensation reaction is an acid or basecatalyzed polymerization that produce(s) water, an alcohol, and/or anamine as a by-product.

The guanidyl copolymer can have a weight average molecular weight in arange of about 1,000 Dalton (D), 2,000 D, 3,000 D, 4,000 D, 5,000 D,6,000 D, 7,000 D, 8,000 D, 9,000 D, or 10,000 D to about 5,000 D, 10,000D, 15,000 D, 20,000 D, 25,000 D, 50,000 D, 75,000 D, 100,000 D, or1,000,000 D. Preferably, the weight average molecular weight is in therange of about 1,000 D to about 30,000 D, more preferably about 1,000 Dto about 20,000 D. The guanidyl copolymer can further have a degree ofbranching of about 10 to about 90%. The guanidyl copolymer is preferablya cationic polymer, and maintains a level of cationicity up to a pH ofabout 9, about 10, about 11, or about 12. In one embodiment, thecationicity of the polymer, as measured in milliequivilents per gram,varies by less than about 75%, more preferably less than about 50% froma pH of about 3 to a pH of about 10.

The guanidyl copolymer can be made by the condensation of an aminereactant selected from dicyanodiamine, guanamine, guanidine, melamine,cyanamine, guanylurea, or a mixture thereof; and a carbonyl reactantselected from formaldehyde, paraformaldehyde, urea, thiourea, glyoxal,acetaldehyde, propionaldehyde, butrylaldehyde, glutaraldehyde, acetone,or a mixture thereof.

The guanidyl copolymer can be made, for example, from about 1 wt. % toabout 95 wt. %, about 10 wt. % to about 40 wt. %, or 10 wt. % to 40 wt.% guanidyl reactant; about 0 wt. % to about 95 wt. %, about 10 wt. % toabout 40 wt. %, or 10 wt. % to 40 wt. % functional amine reactant; about1 wt. % to about 98 wt. %, about 10 wt. % to about 40 wt. %, or 10 wt. %to 40 wt. % water-soluble salt; and about 1 wt. % to about 98 wt. %,about 10 wt. % to about 40 wt. %, or 10 wt. % to 40 wt. % carbonyl orimine reactant.

In a particular embodiment, the guanidyl copolymer is the condensationproduct of an amino base, formaldehyde, an alkylenepolyamine, and theammonium salt of an inorganic or organic acid. Condensates of this typeare well known and are described in U.S. Pat. Nos. 3,106,541, 3,410,649,3,582,461, and 4,383,077, the disclosures of which are incorporatedherein by reference. The condensate can also be made at a neutral oralkaline pH, for example those condensation products described in U.S.Pat. No. 3,015,649 which is incorporated herein by reference.

The guanidyl reactant can be selected from a group consisting ofguanidine, guanidine salts, cyanamide, dicyanamide, biguanide,guanylurea, guanylthiourea, polycyclic guanidine,N-(4-aminobutyl)guanidine, 2-amino-5-guanidinopentanoic acid,imidodicarbonimidic diamide, (N-butylimidocarbonimidic diamide),(2-(methylguanidino) ethanoic acid), (2-[carbamimidoyl(methypamino]ethyldihydrogen phosphate), cyanoguanidine, (2-guanidinoacetic acid),(3-(diaminomethylideneamino)propanoic acid),(N,N-dimethylimidodicarbonimidic diamide), (1-nitroguanidine),(4-amino-N-[amino(imino)methyl]benzenesulfonamide),(2-[10-(diaminomethylideneamino) decyl]guanidine dihydrochloride),melamine, alkyl guanidine, aryl guanidine, alkylaryl guanidine, alkylbiguanide, aryl biguanide, alkylaryl biguanide and combinations, salts,derivatives thereof and mixtures thereof. In another embodiment, theguanidyl reactant can be selected from the group consisting ofguanidine, 2-cyanoguanidine, and a mixture thereof. In still anotherembodiment, the guanidyl reactant can be selected from the groupconsisting of guanidine, guanidine salts, biguanide, cyanoguanidine,melamine, and a mixture thereof.

The carbonyl reactant can be selected from a group of compounds thathave a carbonyl functional group, for example, an aldehyde, a ketone, aurea, an amide, and a mixture thereof. Examples of carbonyl reactantsinclude formaldehyde, acetaldehyde, paraformaldehyde, trioxane, urea,thiourea, glyoxal, acetaldehyde, propionaldehyde, butrylaldehyde,glutaraldehyde, acetone, and/or a formaldehyde source materials (e.g.,hexamethylenetetramine). The carbonyl reactant can further includeprotected aldehydes, e.g., acetals. The imine reactant, for example, canbe an aldimine, ketimine, imidate, amidate, or a mixture thereof.

The guanidyl copolymer can further include a functional amine reactant.Herein, a functional amine reactant can be an alkylenepolyamine havingthe formula (alkyl)_(x)(amine)_(y) where the alkyl is selected from thegroup consisting of ethyl, propyl, butyl, pentyl, hexyl, and a mixturethereof, where x is in a range from 1 to 10, and y is in a range of 2 to11; an aminoethylpiperizine; an alkanolamine; and a mixture thereof. Forexample, the alkylenepolyamine can be ethylenediamine,diethylenetriamine, triethylenetetramine, propylenediamine,dipropylenetriamine, ethylene propylene triamine, ethylene dipropylenetetramine, diethylene propylene tetramine, ethylene tripropylenepentamine, butylenediamine, pentylenediamine, hexamethylenediamine,tetraethylenepentamine, 1,2-propylenediamine, dibutylenetriamine,tributylenetetramine, tetrabutylenepentamine, dipentylenetriamine,tripentylenetetramine, tetrapentylenepentamine, and a mixture thereof.The functional amine reactant can be an alkylamine, alkyldiamine,alkenepolyamine, polyoxyalkylamine or diamine, alkanolamine (e.g.,mono/di/tri ethanolamine) or a combination thereof. Additionalfunctional amine reactants are described as aminopolymers in OrganicPolymer Chemistry, 2nd ed., Chapman and Hall, 1988, pp. 341-357, andincorporated herein by reference.

The stabilization agent can further include a water-soluble salt. Watersoluble salts include those salts with a cation selected from the groupconsisting of an ammonium ion, an alkali metal ion, an alkaline earthmetal ion and a mixture thereof; and an anion. Examples include NaF, KF,NH₄Cl, LiCl, NaCl, KCl, RbCl, MgCl₂, CaCl₂, SrCl₂, NH₄Br, LiBr, NaBr,KBr, RbBr, MgBr₂, CaBr₂, SrBr₂, and other salts where the anion can bean oxyanion (e.g., formate, succinate, sulfite, sulfate, nitrite,nitrate, hydroxide, oxide, chlorite, and perchlorate). Preferably, thewater-soluble salt is selected from the group consisting of KCl, MgCl₂,CaCl₂ and mixtures thereof. In one embodiment, the water-soluble saltcan be obtained from a subterranean formation, for example, through thedissolution of the water-soluble salt in fracturing fluids. Herein, thefracturing fluids can be recycled or reused without removing thedissolved water-soluble salts. Additionally, the concentration of thewater-soluble salt in the fracturing fluid can be increased through theadmixing of an additional water-soluble salt with a recycled fracturingfluid or admixing a stabilization agent that includes water-soluble saltand the guanidyl copolymer with the recycled fracturing fluid.

The guanidyl copolymer and water-soluble salt can be mixed in a weightratio of about 10:1 to about 1:10, about 5:1 to about 1:5, or about 1:1to about 1:3, grams guanidyl copolymer to grams water-soluble salt. Theammonium salts include the reaction products of ammonium hydroxideand/or ammonia and hydrochloric, sulfuric, phosphoric, boric, formic,acetic, glycolic, propionic, and/or butyric acid.

In accordance with the compounds, compositions, and methods describedherein, the reduction of clay swelling and/or fines migration in asubterranean formation can be accomplished by contacting thesubterranean formation with a stabilization agent or composition thatcomprises a guanidyl copolymer. Contacting the subterranean formationcan be accomplished, for example, by providing the stabilization agentor guanidyl copolymer-containing composition to the subterraneanformation before, during, or after hydraulic fracturing or drilling. Forexample, the stabilization agent can be mixed with the fracturing fluid,often prior to fracturing. The fracturing fluid-stabilizationagent-containing mixture can then be used to fracture a subterraneanformation. In one embodiment, the stabilization agent is included in thefracturing fluid in an amount in a range of about 50 ppm to about 50,000ppm, about 100 ppm to about 37,000 ppm, about 150 ppm to about 25,000ppm, about 150 ppm to about 12,000 ppm, about 200 ppm to about 6,000ppm, or about 300 ppm to about 2,600 ppm,based on the total weight ofthe fracturing fluid . The water soluble salt can be included in thefracturing fluid in an amount in a range of about 100 ppm to about20,000 ppm, about 100 ppm to about 5,000 ppm, or about 100 ppm to about2,000 ppm and the guanidyl copolymer can be included in the fracturingfluid in an amount in a range of about 50 ppm to about 5,000 ppm, about100 ppm to about 1,000 ppm, or about 200 ppm to about 600 ppm, based onthe total weight of the fracturing fluid. The fracturing fluids canfurther include, for example, proppants, friction reducers,disinfectants and/or salts.

In another embodiment, the materials and method of stabilizing asubterranean formation can be provided as a kit that includes asufficient quantity of a guanidyl copolymer, fracturing fluid, and awater-soluble salt for on-site admixture with water, and, optionally,other stabilization components to stabilize the subterranean formation.

In another embodiment, the fracturing fluids described herein include afriction reducer; preferably, the stabilization agent includes thefriction reducer. Typical friction reducer systems include an anionicfriction reducer (e.g., a very high molecular weight (10 million to 20million D) acrylamide/sodium acrylate copolymer) and further includeanionic polyelectrolyte(s) which have a molecular weight of less thanabout 10,000 D and can be selected from the group consisting ofpolyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate,partially hydrolyzed polyacrylamide, polyvinyl alcohol, polyvinylacetate, polyvinylpyrrolidone and copolymers of maleic anhydride andacrylate monomers. Unlike the typical prior art friction reducercompositions, the herein presented methods and compositions preferablyinclude a cationic friction reducer (e.g., a very high molecular weightpolymer having a cationic charge; examples include but are not limitedto acrylamide/dimethylaminoethyl acrylate-methyl chloride quaternarycopolymers, quaternized guars, and guar gums). Preferably, the cationicfriction reducer is a cationic polyacrylamide copolymer, preferably,having about 5 to about 35 mol % ammonium monomer units. Examples ofcationic friction reducers include, but are not limited to, KemEflowC-4102, KemEflow C-4107, and KemEflow C-4604 (available from KEMIRA,Helsinki, Finland); FR-48W Friction Reducer (available from HALLIBURTON,Houston Tex., USA); OILAID-AFR-1, OILAID-FR-20, and OILAID-FR-30(available from MESSINA INC., Dallas Tex., USA), and those cationicfriction reducers disclosed in U.S. Pat. No. 6,787,506, incorporatedherein by reference. The amount of cationic friction reducer used isbetween about 10 ppm to about 10,000 ppm, preferably about 100 to about5,000 ppm, more preferably about 250 ppm to about 2,500 ppm, and evenmore preferably about 500 ppm to about 1,500 ppm, based on the totalweight of the fracturing fluid.

Unexpectedly, the combination of the herein disclosed guanidyl copolymerand cationic friction reducer allows for significant reductions in theamount of friction reducer employed. For example, the guanidyl copolymerallows for a reduction of about 10% to about 90%, in some embodimentsabout 20% to about 80%, or about 30% to about 70% in the total dosage ofthe friction reducer added to the fracturing fluid. In one example,prior art friction reducer compositions may add 1 gallon of an anionicfriction reducer per 1,000 gallons of water to achieve a predeterminedlevel of friction reduction;with the compositions described herein,about 0.55 gallons, about 0.65 gallons, or about 0.75 gallons ofcationic friction reducer can be added to 1,000 gallons of water toachieve the same predetermined level of friction reduction. Thisreduction in the amount of friction reducer necessary to achieve apredetermined level of friction reduction is, preferably, a reduction ofat least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80%, and can leadto a significant cost savings over traditional compositions.

The result of the stabilization of the subterranean formation with thestabilization agent and compositions described herein is thatparticulates loosened from the subterranean formation by the process ofremoving the hydrocarbon product have reduced swell, have reducedsubterranean migration, do not reduce the flow of the hydrocarbonproduct, and/or do not contaminate the hydrocarbon product. Without thestabilization agent, clays and/or fines can swell and/or migrate toinhibit and contaminate the hydrocarbon production. The stabilizationeffect can be measured by comparing wells with and without thestabilization agent or comparing the flow rate of fluids (e.g., oil,water or natural gas) through samples from the same subterraneanformation with and without the stabilization agent.

Subterranean formations can be stabilized by contacting them with theabove described guanidyl copolymer. In one embodiment, clay swellingand/or fines migration in a subterranean formation can be reduced bycontacting the subterranean formation with a stabilization agent thatcomprises a guanidyl copolymer; and contacting the subterraneanformation with a cationic friction reducer. The guanidyl copolymer andthe cationic friction reducer can be pre-mixed and then directed intocontact with the subterranean formation or alternatively, the guanidylcopolymer and the cationic friction reducer can be individually appliedto, or provided to, the subterranean formation. The applied guanidylcopolymer can comprise the reaction product of a guanidyl reactant and acarbonyl reactant; wherein the carbonyl reactant is selected from thegroup consisting of an aldehyde, a ketone, a urea, an amide, and amixture thereof; and wherein the guanidyl reactant is selected from thegroup consisting of guanidine, guanidine salt, cyanamide, dicyanamide,biguanide, guanylurea, guanylthiourea, polycyclic guanidine,N-(4-aminobutyl)guanidine, 2-amino-5-guanidinopentanoic acid,imidodicarbonimidic diamide, (N-butylimidocarbonimidic diamide),(2-(methylguanidino) ethanoic acid),(2-[carbamimidoyl(methyl)amino]ethyl dihydrogen phosphate),cyanoguanidine, (2-guanidinoacetic acid),(3-(diaminomethylideneamino)propanoic acid),(N,N-dimethylimidodicarbonimidic diamide), (1-nitroguanidine),(4-amino-N-[amino(imino)methyl]benzenesulfonamide),(2-[10-(diaminomethylideneamino)decyl]guanidine dihydrochloride),melamine, alkyl guanidine, aryl guanidine, alkylaryl guanidine, alkylbiguanide, aryl biguanide, alkylaryl biguanide, and a mixture thereof.Preferably, the guanidyl reactant is selected from the group consistingof guanidine, 2-cyanoguanidine, and a mixture thereof.

Preferably, the cationic friction reducer is selected from the groupconsisting of acrylamide/dimethylaminoethyl acrylate-methyl chloridequaternary copolymer, quaternized guar, guar gum, and mixtures thereof.

Contacting the subterranean formation with the stabilization agent andfriction reducer can include providing the stabilization agent to thesubterranean formation as a mixture with a suitable carrier, optionallyas a mixture with the friction reducer and carrier. One example of acarrier for the stabilization agent is water.

In another embodiment, a (previously) hydraulically fracturedsubterranean formation can be restabilized by contacting thehydraulically fractured subterranean formation with a stabilizationagent that comprises a guanidyl copolymer. The hydraulically fracturedsubterranean formation can be any hydraulically fractured subterraneanformation, for example, those from which hydrocarbons have beenextracted. Preferably, the hydraulically fractured subterraneanformation is selected from the group consisting of a formation having amineral content that is predominantly clay, shale, sand, and/or amixture thereof. In one preferable embodiment, the hydraulicallyfractured subterranean formation consists of a formation having clay asthe predominant mineral. In another preferable embodiment, thehydraulically fractured subterranean formation consists of a formationhaving shale as the predominant mineral.

The restabilization can include applying the stabilization agent as acomponent in a fracturing fluid (e.g., water), where the guanidylcopolymer comprises about 50 ppm to about 5,000 ppm, about 100 ppm toabout 1,000 ppm, or about 200 ppm to about 600 ppm of the guanidylcopolymer in a fracturing fluid,based on the total weight of thefracturing fluid composition. The restabilization can also includerefracturing the subterranean formation with a fracturing fluid thatcomprises the stabilization agent.

In still another embodiment, the guanidyl copolymer can be used in amethod of flushing a bore hole during drilling with a drilling fluidthat comprises a guanidyl copolymer. The drilling fluid can includeabout 50 ppm to about 5,000 ppm, about 100 ppm to about 1,000 ppm, orabout 200 ppm to about 600 ppm of the guanidyl copolymer,based on thetotal weight of the drilling fluid composition. In one embodiment,flushing a bore hole includes applying the drilling fluid to the drillhead during drilling.

The drilling fluid can be a foaming mud, a water-based mud, an oil-basedmud, or a synthetic-fluid-based mud. The foaming mud is a mixture of agas (e.g., air) and a foaming agent that includes the guanidyl polymer.The water-based mud is a mixture of water, the guanidyl polymer, andoptionally, a thickening agent (preferably a shear-thinning thickeningagent), a viscosity control agent (e.g., a thickener including xanthangum, guar gum, glycol, carboxymethylcellulose, or starch), water-solublesalts, disinfectants, a lubricant, and/or a weighting agent. Theoil-based and synthetic-fluid-based muds include either oil or asynthetic-fluid, the guanidyl polymer and, optionally, a thickeningagent, a viscosity control agent, and/or a weighting agent.

The material being drilled can any subterranean formation, in oneembodiment the method includes drilling a subterranean formation thatcomprises tar sands. In another embodiment the method includes drillinga subterranean formation that comprises a water-swellable clay mineral.

In yet another embodiment, a method of extracting oil from an oilcontaining subterranean formation can include providing, through a firstborehole, a pressurized floodwater (waterflood) that comprises about 50ppm to about 5,000 ppm, about 100 ppm to about 1,000 ppm, or about 200ppm to about 600 ppm of a guanidyl copolymer; and recovering oil fromthe subterranean formation through a second borehole. Preferably, thesubterranean formation was previously hydraulically fractured and oilwas previously extracted.

The composition and application of the pressurized floodwater (e.g., atpressure in a range of about 100 psi to about 1800 psi, about 100 psi toabout 1000 psi, about 100 psi to about 800 psi., about 125 psi to about600 psi, about 150 psi to about 500 psi, at about 250 psi to about 500psi, or at about 250 psi) can be adjusted according to the needs of thesubterranean formation. For example when the subterranean formationcomprises tar sands, the pressurized floodwater can include steam. Inthis embodiment, the guanidyl copolymer can be the reaction product ofan aldehyde reactant selected from the group consisting of formaldehyde,paraformaldehyde, urea, thiourea, glyoxal, acetaldehyde,propionaldehyde, butrylaldehyde, glutaraldehyde, acetone, and a mixturethereof; and a guanidyl reactant is selected from a group consisting ofguanidine, guanidine salt, cyanamide, dicyanamide, biguanide,guanylurea, guanylthiourea, polycyclic guanidine,N-(4-aminobutyl)guanidine, 2-amino-5-guanidinopentanoic acid,imidodicarbonimidic diamide, (N-butylimidocarbonimidic diamide),(2-(methylguanidino)ethanoic acid), (2-[carbamimidoyl(methyl)amino]ethyldihydrogen phosphate), cyanoguanidine, (2-guanidinoacetic acid),(3-(diaminomethylideneamino)propanoic acid),(N,N-dimethylimidodicarbonimidic diamide), (1-nitroguanidine),(4-amino-N-[amino(imino)methyl]benzenesulfonamide),(2-[10-(diaminomethylideneamino)decyl]guanidine dihydrochloride),melamine, alkyl guanidine, aryl guanidine, alkylaryl guanidine, alkylbiguanide, aryl biguanide, alkylaryl biguanide, and a mixture thereof.

Floodwater compositions include the guanidyl copolymer and water (e.g.,the well's produced water). The floodwater can optionally includedisinfectants, oxygen scavenging agents, and/or water-soluble salts, intypically applied amounts.

EXAMPLES

The following examples are provided to illustrate the invention, but arenot intended to limit the scope thereof.

Example 1

Capillary Suction Time (CST) tests were measured as a determination ofthe relative flow capacity of a slurry of ground formation rock used toform an artificial core. The CST test is a common test for materials aswellbore stabilizers and multiple, well known manual and automatedtesting equipment is available for conducting the test, as well known tothose skilled in the art. Here, the mineral sample was ground to a −70mesh grind (U.S. Standard), then 5 grams were placed in 50 ml of a testfluid (the test fluid comprising the stabilization agent and water) andstirred on a magnetic stirrer, in day one trials for 2 hours and in daytwo trials for 24 hours. Then 5 mL of this slurry was placed in acylindrical “mold” setting on top of chromatography paper. The rate ofcapillary flow into the chromatography paper was measured by timing thetime necessary for an observable fluid to from a point 0.25 inches awayfrom the mold to a point one inch away from the mold. The shorter thetime necessary to flow the recorded distance the greater the stabilityof the mineral sample to swelling and/or fines migration. For example, amineral with dispersible or swelling clays would have lower pseudopermeability and will have a longer CST time while one without clay orother fine particles would have a shorter retention time. It cannot beused to examine fluids containing surface active agents.

Here, the data obtained from the CST tests is reported as a CST Ratioobtained from the equation [CST_(sample)−CST_(blank)]/CST_(blank)].Where CST_(blank) is the CST time for the test fluid to flow therequired distance without a mineral sample in the mold.

Capillary Suction Time for samples of Marcellus Shale:

CST Ratio CST Ratio Stabilization Agent Dosage (ppm) Day One Day TwoBlank 0.1 0.1 Fresh Water 4.0 5.8 Comparative Stabilizers Cholinechloride 20,000 3.3 3.3 Choline chloride 2,000 3.5 3.6 Trimethylamine20,000 3.4 3.5 Trimethylamine 2,000 3.6 3.7 Herein Disclosed StabilizerGuanidyl copolymer 300 2.1 2.1

Capillary Suction Time for Samples of Marcellus Shale (With AddedWater-Soluble Salt):

CST Ratio CST Ratio Stabilization Agent Dosage (ppm) Day One Day TwoBlank 0.1 0.1 Fresh Water 4.0 5.8 Water-Soluble Salts Potassium Chloride20,000 1.8 2.8 Potassium Chloride 2,000 3.0 3.2 Magnesium Chloride20,000 3.3 3.8 Magnesium Chloride 2,000 3.0 4.0 Calcium Chloride 20,0003.2 4.4 Calcium Chloride 2,000 3.0 4.3 Comparative Stabilizer(A)—polyEPDMA Poly EPDMA 300 2.5 2.5 Poly EPDMA 300 2.3 4.2 PotassiumChloride 2,500 Poly EPDMA 300 2.8 2.8 Calcium Chloride 1,200 ComparativeStabilizer (B)—polyDADMAC Poly DADMAC 300 2.0 2.1 Poly DADMAC 300 2.73.5 Potassium Chloride 2,500 Poly DADMAC 300 2.3 2.3 Calcium Chloride1,200 Herein Disclosed Stabilizer Guanidyl Copolymer 300 2.1 2.1Guanidyl Copolymer 300 1.8 3.0 Potassium Chloride 2,500 GuanidylCopolymer 300 1.8 2.0 Calcium Chloride 1,200 Guanidyl Copolymer 300 1.82.2 Magnesium Chloride 1,500

Example 2

Roller Oven Shale Stability data were obtained using a modified API RP13i procedure. Here, the shale is ground to a particle size less than 2mm (10 mesh) and larger than 0.425 mm (40 mesh). The particles are splitequally using a spinning Riffler then distributed equally into 10 gmsamples. The number of samples depends on the number of fluids to betested. The weighed sample is placed in a glass bottle along with 50 mlof the test fluid and allowed to roll in a roller oven at a desiredtemperature. The samples are then screened through 70 mesh screen (0.269mm) and washed with deionized water prior to drying and reweighing. Theamount of sample pass through the 70 mesh screen is the measure ofinstability of the shale. The higher the percentage of solids passedthrough the 70 mesh screen, the lower the stability of the shale in thatparticular fluid.

The mass of sample passed through 70 mesh screen (0.269 mm) is expressedas a mass fraction in percent, M_(p)=(M_(I)−M_(F))/M_(I)*100; M_(p)=Massof shale passed through 70 mesh screen, M_(I)=Initial mass of shalesample, M_(F)=Final dry mass of shale sample.

Roller Oven Shale Stability Marcellus Shale:

Dosage (ppm) % Solids Not Retained Fresh Water — 5.9 ComparativeStabilizers Choline chloride 20,000 5.0 Choline chloride 2,000 5.4Trimethylamine 20,000 5.3 Trimethylamine 2,000 5.6 Herein DisclosedStablizer Guanidyl copolymer 300 3.3

Roller Oven Shale Stability Marcellus Shale (With Water-Soluble Salt):

Dosage (ppm) % Solids Not Retained Fresh Water — 5.9 Water-Soluble SaltsPotassium Chloride 20,000 4.8 Potassium Chloride 2,000 5.3 CalciumChloride 20,000 4.6 Calcium Chloride 2,000 4.5 Lithium Chloride 12,0005.3 Lithium Chloride 1,500 6.2 Magnesium Chloride 30,000 4.7 MagnesiumChloride 5,000 4.1 Magnesium Sulfate 30,000 5.5 Magnesium Sulfate 5,0005.3 Cesium Chloride 40,000 4.3 Cesium Chloride 6,000 4.9 Cholinechloride 20,000 5.0 Choline chloride 2,000 5.4 Trimethylamine 20,000 5.3Trimethylamine 2,000 5.6 Comparative Stabilizer (A)—polyEPDMA Poly EPDMA300 3.5 Poly EPDMA 300 3.9 Calcium Chloride 1,000 Comparative Stabilizer(B)—polyDADMAC Poly DADMAC 300 3.7 Poly DADMAC 300 3.6 Calcium Chloride1,000 Herein Disclosed Stabilizer Guanidyl Copolymer 300 3.3 GuanidylCopolymer 300 2.9 Calcium Chloride 1,000

Example 3

Core tests were obtained to verify the performance of the hereindisclosed guanidyl copolymers. A 1 in. diameter drilled core sample washorizontally fractured (most often along a bedding plane) and the coresample was placed in a Hassler sleeve core holder for flow studies. Thepermeability of the core samples were then measured (in microdarcy(□d)). First, the core sample was exposed to hexane (conductivity was6.47 □d-ft), then a brine solution having 600 ppm guanidyl copolymer wasadded and the conductivity decreased to 0.47 □d-ft (an expected changedue to the transition from a non-wetting to wetting solution). Next, thecore sample was flushed with fresh water and a conductivity of 0.42□d-ft was measured, suggesting stability of the core sample. Notably,core samples tested with only a temporary clay stabilizer pluggedimmediately upon flushing with fresh water and no conductivity datacould be obtained.

Example 4

Friction Reduction: the pressure and percent friction reduction forcomparative and herein describes materials were obtained using afriction loop apparatus. The friction loop apparatus was a closed looppipeline designed to measure pressure drop across a 35 foot section of astainless steel pipe having a 0.54 inch nominal diameter. The frictionloop was operated at a flow rate of 16 gallons per minute, a startingtemperature of about 80° F., a pipe roughness factor of 1×10⁻⁵ inches.This friction loop generated Reynolds numbers in a range of 50,000 to70,000 at a flow rate of 10 gallons per minute and a range of 120,000 to140,000 at 16 gallons per minute. Differential pressure was continuallymeasured across the test section at one-second intervals for a period ofabout 35 minutes. The first minute of the test was used to establish abaseline pressure drop. The pressure drop across the thirty five (35)foot section of pipe for the water was calculated from the flow rate andpipe dimensions in accordance with the flowing formula:

${\Delta \; P_{water}} = \frac{\rho \; V^{2}L\; f}{2g_{c}D_{h}}$

wherein ΔP° _(water) is the calculated pressure drop for water, ρ isdensity, V is the velocity, L is length, g_(c) is the gravitationalconstant, and D_(h) is the pipe diameter. The variable f was calculatedin accordance with the formula for turbulent flow below:

$f = \left\{ {{- 2}{\log \left\lbrack {\frac{ɛ/d}{3.7} - {\frac{5.02}{N_{Re}}{\log \left( {\frac{ɛ/d}{3.7} - \frac{14.5}{N_{Re}}} \right)}}} \right\rbrack}} \right\}^{- 2}$

wherein the variable ε is the pipe roughness, the variable d is the pipediameter, and the variable N_(Re) is the Reynolds Number.

Following addition of the particular friction reducing composition tothe tank, the measured was compared to the calculated pressure drop forwater to determine a percent friction reduction in accordance with theequation:

${\% \mspace{20mu} F\; R} = \frac{{\Delta \; P_{solvent}} - {\Delta \; P_{solution}}}{\Delta \; P_{solvent}}$

wherein % FR is the percent friction reduction, ΔP_(solvent) is thepressure drop across the test section for pure solvent (water or testbrine), and ΔP_(solution) is the pressure drop across the test sectionfor the solution of water or test brine, and friction reducer.

Results are presented in the following tables:

Comparative pipe pressures for Anionic Friction Reducer (FLOPAM DR-7000available from SNF, Inc., Riceboro, Ga., USA)over 35 minutes

Anionic Choline Calcium 5 20 35 Friction Reducer Chloride ChlorideMinutes Minutes Minutes 300 ppm 60 psi 64 psi  70 psi 300 ppm 1500 ppm59 psi 64 psi  70 psi 300 ppm 1500 ppm 1000 ppm 75 psi 100 psi  120 psi150 ppm 60 psi 82 psi 120 psi 150 ppm 1500 ppm 59 psi 81 psi 120 psi 150ppm 1500 ppm 1000 ppm 85 psi 140 psi  170 psi

Comparative percent friction reduction for Anionic Friction Reducer(FLOPAM DR-7000 available from SNF, Inc., Riceboro, Ga., USA) over 35minutes

Anionic Choline Calcium 5 20 35 Friction Reducer Chloride ChlorideMinutes Minutes Minutes 300 ppm 74% 72% 68% 300 ppm 1500 ppm 75% 72% 68%300 ppm 1500 ppm 1000 ppm 70% 55% 47% 150 ppm 74% 60% 50% 150 ppm 1500ppm 75% 60% 50% 150 ppm 1500 ppm 1000 ppm 60% 40% 30%

Pipe Pressures for Herein-Described System (using CALLAWAY C4802 as thecationic friction reducer, available from KEMIRA) over 35 minutes

Cationic Guanidyl Calcium 5 20 35 Friction Reducer Copolymer ChlorideMinutes Minutes Minutes 200 ppm 60 psi 66 psi  72 psi 200 ppm 1000 ppm61 psi 68 psi  74 psi 200 ppm 900 ppm 59 psi 65 psi  70 psi 200 ppm 900ppm 1000 ppm 59 psi 63 psi  68 psi 150 ppm 60 psi 85 psi 120 psi 150 ppm1000 ppm 60 psi 87 psi 125 psi 150 ppm 900 ppm 60 psi 72 psi 110 psi 150ppm 900 ppm 1000 ppm 60 psi 75 psi 100 psi

Percent Friction Reduction for Herein-Described System (using CALLAWAYC4802 as the cationic friction reducer, available from KEMIRA) over 35minutes

Cationic Guanidyl Calcium 5 20 35 Friction Reducer Copolymer ChlorideMinutes Minutes Minutes 200 ppm 74% 72% 66% 200 ppm 1000 ppm 73% 70% 64%200 ppm 900 ppm 75% 73% 68% 200 ppm 900 ppm 1000 ppm 75% 74% 70% 150 ppm74% 58% 50% 150 ppm 1000 ppm 74% 57% 45% 150 ppm 900 ppm 74% 66% 52% 150ppm 900 ppm 1000 ppm 74% 62% 55%

The foregoing description is given for clearness of understanding only,and no unnecessary limitations should be understood therefrom, asmodifications within the scope of the invention may be apparent to thosehaving ordinary skill in the art.

1-21. (canceled)
 22. A stabilization agent comprising: an admixture of a guanidyl copolymer and a water-soluble salt in a ratio of about 10:1 to about 1:10, grams guanidyl copolymer to grams water-soluble salt; wherein the guanidyl copolymer is the condensation product of a guanidyl reactant t selected from the group consisting of guanidine, guanidine salt, cyanamide, dicyanamide, biguanide, guanylurea, guanylthiourea, polycyclic guanidine, N-(4-aminobutyl)guanidine, 2-amino-5-guanidinopentanoic acid, imidodicarbonimidic diamide, (N-butylimidocarbonimidic diamide), (2-(methylguanidino) ethanoic acid), (2-[carbamimidoyl(methyl)amino]ethyl dihydrogen phosphate), cyanoguanidine, (2-guanidinoacetic acid), (3-(diaminomethylideneamino)propanoic acid), (N,N-dimethylimidodicarbonimidic diamide), (1-nitroguanidine), (4-amino-N-[amino(imino)methyl]benzenesulfonamide), (2-[10-(diaminomethylideneamino)decyl]guanidine dihydrochloride), melamine, alkyl guanidine, aryl guanidine, alkylaryl guanidine, alkyl biguanide, aryl biguanide, alkylaryl biguanide, and a mixture thereof and a carbonyl reactant; and a carbonyl reactant selected from the group consisting of an aldehyde, a ketone, a urea, an amide, and a mixture thereof; and wherein the water-soluble salt is selected from the group consisting of potassium chloride, magnesium chloride, calcium chloride, and a mixture thereof.
 23. The stabilization agent of claim 22, further comprising a cationic friction reducer admixed with the guanidyl copolymer in a weight ratio of about 1:4 to about 10:1, cationic friction reducer to guanidyl copolymer.
 24. The method of claim 22, wherein the weight ratio is about 5:1 to about 1:5.
 25. The method of claim 24, wherein the weight ratio is about 1:1 to about 1:3. 26-34. (canceled)
 35. A method of extracting oil from an oil containing subterranean formation comprising: providing, through a first borehole, a pressurized floodwater that comprises about 50 ppm to about 5,000 ppm guanidyl copolymer; and recovering oil from the subterranean formation through a second borehole; wherein the guanidyl copolymer is the condensation product of a guanidyl reactant t selected from the group consisting of guanidine, guanidine salt, cyanamide, dicyanamide, biguanide, guanylurea, guanylthiourea, polycyclic guanidine, N-(4-aminobutyl)guanidine, 2-amino-5-guanidinopentanoic acid, imidodicarbonimidic diamide, (N-butylimidocarbonimidic diamide), (2-(methylguanidino) ethanoic acid), (2-[carbamimidoyl(methyl)amino]ethyl dihydrogen phosphate), cyanoguanidine, (2-guanidinoacetic acid), (3-(diaminomethylideneamino)propanoic acid), (N,N-dimethylimidodicarbonimidic diamide), (1-nitroguanidine), (4-amino-N-[amino(imino)methyl]benzenesulfonamide), (2-[10-(diaminomethylideneamino)decyl]guanidine dihydrochloride), melamine, alkyl guanidine, aryl guanidine, alkylaryl guanidine, alkyl biguanide, aryl biguanide, alkylaryl biguanide, and a mixture thereof and a carbonyl reactant; and a carbonyl reactant selected from the group consisting of an aldehyde, a ketone, a urea, an amide, and a mixture thereof.
 36. The method of claim 34, wherein the subterranean formation was previously hydraulically fractured and oil was previously extracted.
 37. The method of claim 34, wherein the pressurized floodwater comprises steam.
 38. A method comprising: flushing a bore hole during drilling with a drilling fluid that comprises a guanidyl copolymer; wherein the guanidyl copolymer is the condensation product of a guanidyl reactant t selected from the group consisting of guanidine, guanidine salt, cyanamide, dicyanamide, biguanide, guanylurea, guanylthiourea, polycyclic guanidine, N-(4-aminobutyl)guanidine, 2-amino-5-guanidinopentanoic acid, imidodicarbonimidic diamide, (N-butylimidocarbonimidic diamide), (2-(methylguanidino) ethanoic acid), (2-[carbamimidoyl(methyl)amino]ethyl dihydrogen phosphate), cyanoguanidine, (2-guanidinoacetic acid), (3-(diaminomethylideneamino)propanoic acid), (N,N-dimethylimidodicarbonimidic diamide), (1-nitroguanidine), (4-amino-N-[amino(imino)methyl]benzenesulfonamide), (2-[10-(diaminomethylideneamino)decyl]guanidine dihydrochloride), melamine, alkyl guanidine, aryl guanidine, alkylaryl guanidine, alkyl biguanide, aryl biguanide, alkylaryl biguanide, and a mixture thereof; an amine reactant; and a carbonyl reactant selected from the group consisting of an aldehyde, a ketone, a urea, an amide, and a mixture thereof.
 39. The method of claim 37, wherein the drilling fluid comprises about 50 ppm to about 5,000 ppm guanidyl copolymer.
 40. The method of claim 37, wherein the drilling fluid comprises about 100 ppm to about 1,000 ppm guanidyl copolymer.
 41. The method of claim 37, wherein the drilling fluid comprises about 200 ppm to about 600 ppm guanidyl copolymer.
 42. The method of claim 37 further comprising: drilling a subterranean formation that comprises a water-swellable clay mineral.
 43. The method of claim 37, wherein flushing a bore hole comprises applying the drilling fluid to the drill head during drilling.
 44. The method of claim 38, further comprising a cationic friction reducer admixed with the guanidyl copolymer in a weight ratio of about 1:4 to about 10:1, cationic friction reducer to guanidyl copolymer.
 45. The method of claim 44, wherein the weight ratio is about 5:1 to about 1:5.
 46. The method of claim 45, wherein the weight ratio is about 1:1 to about 1:3.
 47. A method comprising: flushing a bore hole during drilling with a drilling fluid that consists of a pressurized floodwater, a friction reducer and a guanidyl copolymer; wherein the guanidyl copolymer is the condensation product of a guanidyl reactant t selected from the group consisting of guanidine, guanidine salt, cyanamide, dicyanamide, biguanide, guanylurea, guanylthiourea, polycyclic guanidine, N-(4-aminobutyl)guanidine, 2-amino-5-guanidinopentanoic acid, imidodicarbonimidic diamide, (N-butylimidocarbonimidic diamide), (2-(methylguanidino) ethanoic acid), (2-[carbamimidoyl(methyl)amino]ethyl dihydrogen phosphate), cyanoguanidine, (2-guanidinoacetic acid), (3-(diaminomethylideneamino)propanoic acid), (N,N-dimethylimidodicarbonimidic diamide), (1-nitroguanidine), (4-amino-N-[amino(imino)methyl]benzenesulfonamide), (2-[10-(diaminomethylideneamino)decyl]guanidine dihydrochloride), melamine, alkyl guanidine, aryl guanidine, alkylaryl guanidine, alkyl biguanide, aryl biguanide, alkylaryl biguanide, and a mixture thereof; an amine reactant; and a carbonyl reactant selected from the group consisting of an aldehyde, a ketone, a urea, an amide, and a mixture thereof.
 48. The method of claim 47, wherein the friction reducer comprises a cationic polyacrylamide copolymer having about 5 to about 35 mol % ammonium monomer units. 